Fundamentals of Energy-Science and Technology

Any physical activity in this world, whether carried out by human beings or by nature, is caused due to flow of energy in one form or the other. Energy is required to do any kind of work. The word 'energy' itself is derived from the Greek word 'en-ergon', which means 'in-work' or 'work content'. The work output depends on the energy input. The capability to do work depends on the amount of energy one can control and utilize. Energy is the most basic infrastructure input for economic growth and development of a country. Before the industrial revolution that started around 200 years ago, people were essentially dependent on manual and animal labour. Human and animal energy requirements were met through food intake. Life was simple and unsophisticated, and the environment was relatively clean. Then in 1785,the invention of the steam engine by James Watt of Scotland brought the industrial revolution. It was the beginning of a mechanical age or the age of machines. The advent of the internal combustion engine in the late nineteenth century gave a further momentum to the trend. Gradually, the industrial revolution spread to the whole world. In 1888, Nickola Tesla invented the commercial induction motor. The introduction of electrical machines along with the commercial availability of electrical power started the new electrical age. AII this led to an increase of energy requirement by leaps and bounds. Energy has been the lifeblood for continual progress of the human civilization. Thus, with developments in the human living standard, the energy consumption also accelerated.

ENERGY CONSUMPTION

AND STANDARD OF LIVING

The energy consumption of a nation can be broadly clivided into the following areas or sectors depending on energy-related activities. These can further be subclivided into subsectors: • • • • Domestic sector (houses and ofíices including commercial builclings) Transportation sector Agriculture sector Industry sector

1.1

Consumption of a large amount of energy in a country inclicates increased activities in these sectors. This may imply better comforts at home due to use of various appliances, better transport facilities and more agricultural and industrial production. All this amounts to a better quality of life. Therefore, the per capita energy consumption of a country is an index of the standard of living or

Non-conventional

Energy Resources

,

.

prosperity (i.e, income) of the people of the country. InTable 1.1, the comparative data of the annual primary energy consumptions of some countries are given to emphasize this point.
Table
1.1

At present (year 2005) the total annual energy consumption of the world is estimated as 500 exajoules. Out of which 26% energy is consumed by USA, which has about 5% of the world's population, while India which houses 17% of the world's population consumes only 3.3% of the total world energy. This mismatch reflects in the negative differential in the quality of life of the people in these countries. Electricity is considered a necessary requirement for economic and social development of a country. For the year 2007, the annual per capita electrical-energy consumption in USA was 12,133 kWh and that in India it was 702 kWh. OIL CRISIS OF 1973 The year 1973 brought an end to the era of secure and cheap oil. In October of that year, OPEC (Organization of Petrol Exporting Countries, founded in 1960) put an embargo on oil production and started the oil-pricing control strategy. Oil prices shot up fourfold causing asevere energy crisis the world overo This .resulted in spiraling price rise of various commercial energy sources, further leading to global inflation. Governments of all countries took this matter very seriously and for the first time, a need for developing alternative sources of energy was felt. Alternate energy sources were given serious consideration and huge funds were allocated for the development of these resources. Thus, the year 1973 is considered as the year of the first 'oil shock'. In the same decade, one more 'oil shock' jolted the world in 1979, which further focussed the attention on alternate energy sources. By the end of 1980, the price of crude oil stood at 19 times what it had been just ten years earlier. CLASSIFICATION OF ENERGY RESOURCES

1.2

Energy resources can be classified in the following ways.

Fundamentals of Energy-Science and Technology

L~

~

1.

Based on Usability of Energy

(a) Primary Resources These are resources embodied in nature prior to undergoing any human made conversions or transformations. Examples of primary energy resources are coal, crude oil, sunlight, wind, running rivers, vegetation, uranium, etc. These resources are generally available in raw forms and are, therefore, known as raw energy resources. Generally, this form of energy cannot be used as such. These are located, explored, extracted, processed and are converted to a form as required by the consumer. Thus, some energy is spent in making the resource available to a user in a usable formo The energy yield ratio of an energy extraction process is defined as follows: Energy received from raw energy source Energy spent to obtain raw energy source

Energy yield ratio

Only resources for which the energy yield ratio is fairly high are considered worthy of exploration.
(b) Intermediate Resources These are obtained from primary energy by one or more steps of transformation and are used as vehicles of energy.

(e) Secondary Resources The form of energy which is finally supplied to a consumer for utilization is known as secondary or usable energy, e.g., electrical energy, thermal energy (in the form of steam or hot water), chemical energy (in the form of hydrogen or fossil fuels), etc. Some forms of energy may be categorized both in intermediate secondary resources, e.g., electricity and hydrogen.
2.

as well as

Based on Traditional

Use

(a) Conventiona/ Energy resources which are being traditionally used for many decades and were in common use around the oil crisis of 1973, are called conventional energy resources, e.g., fossil fuels, nuclear and hydro resources. (b) Non-conventiona/ Energy resources which are considered for large-scale use after the oil crisis of 1973, are called non-conventional. energy sources, e.g., solar, wind, biomass, etc.

3.
(a)

Based on Long-term
Non-renewab/e

Av·ailability

their consumption

Resources which are finite and do not get replenished after are called non-renewable, e.g., fossil fuels, uranium, etc.

(b) Renewab/e Resources which are renewed by nature again and again and their supply is not affected by the rate of their consumption are called renewable, e.g., solar, wind, biomass, ocean (thermal, tidal and wave) , geothermal, hydro, etc.

--

_._---

.__

._----------

. Non-conventronc I

I Energy Respurces

4· (a)

Based on Commercial

Application

Commercia/ Energy Resource The secondary

usable energy forms such as electricity, petrol, diesel, gas, etc., are essential for commercial activities and are categorized as commercial energy resources. The economy of a country depends on its ability to convert natural raw energy into commercial energy.

(b)

Non-commercia/ Energy The energy derived from nature and used directly without passing through a commercial outlet is called a non-commercial resource, e.g., wood, animal dung cake, crop residue, etc.

The average percentage consumption trend of various primary energy resources of the world is indicated in Fig. 1.1, though the trend differs from country to country. Looking at this figure, the heavy dependence on fossil fuels stands out clearly. About 86% of the world's energy supply comes mainly from fossil fuels. The share of fossil fuels is more than 90% in India.

1.4

TREN O OF PRIMARV ENERGV RESOURCES

0iI

37.5%

Renewables Biomass Solar heat Geothermal Solar PV Hydro Wind Biofuel

4% 0.5% 0.2% 0.05% 3% 0.3% 0.2%
2005

Fig. 1.1 Percentage consumption

of various primary energy resources (year

data)

~
Fundamentals

of Energy-Science

and Technology ~

~

Concern for the environment due to ever-increasing use of fossil fuels and rapid depletion of natural resources have led to development of alternative sources of energy which are renewable and environment friendly. The following points may be mentioned in this connection: 1. The demand of energy is increasing by leaps and bounds due to rapid industrialization and population growth, and hence the conventional sources of energy will not be sufficient to meet the growing demando Conventional sources (except hydro) are non-renewable and are bound to finish up one day. Conventional sources (fossil fuels, nuclear) also cause pollution, thereby their use degrades the environment. Large hydro resources affect wildlife, cause deforestation and pose various social problems. In addition to supplying energy, fossil fuels are also used extensively as feed stock materials for the manufacture of organic chernicals. As reserve deplete, the need for using fossil fuels exclusively for such purposes may become greater.

1.5

IMPORTANCE

OF NON-CONVENTIONAL

ENERGY SOURCES

2. 3. 4. 5.

Due to these reasons it has become important to explore and develop non-conventional energy resources to reduce too much dependence on conventional resources. However, the present trend of developments of nonconventional sources indicate that these will serve as supplements rather than substitute for conventional sources for some more time to come. Realising the importance of non-conventional energy sources, in March 1981, the government of India established a Commission for Additional Sources of Energy (CASE) in the Department of Science and Technology, on the lines of the Space and Atornic Energy Comrnissions. In 1982, CASE was incorporated in the newly created Department of Non-Conventional Energy Sources (DNES) under the Ministry of Energy. Also, IREDA (Indian Renewable Energy Development Agency Ltd.) was established in 1987 to promote the development of nonconventional sources. The DNES was later converted to MNES (Ministry of Non-conventional Energy Sources) in 1992. In October 2006, the ministry was re-christened as the Ministry of New and Renewable Energy. India is the only country having a full-fledged rninistry devoted to developing new and renewable energy sources.

Generally, (but not always) we cannot use the energy available from primary energy sources directly. Por example we cannot drive an electric motor from uranium or coal. The energy available from a primary energy source is known as raw energy. This energy undergoes various forms of transformations before

1.6

ENERGY CHAIN

~
Non-conventional Energy Resóurces

•

being utilized finally. The sequence of energy transformations between primary and secondary energy (usable energy) is known as energy chain or energy route. Primary energy Primary energy
--P,~-,-,,;-ng-4 -P-",-"-,,,n-g4

Electrical energy

-T-,,-n,=-,,-'-"n---4

Consumer Consumer

Secondary energy (fuel)

-T-n-n,po-rt-,d-b,-,,,-¡¡/~
road / ocean / pipcline

At present about 30-40% of the world's energy supply is met through the electrical-energy route.

~
Primary energy resource

Non-electric route

f-

f-4Fig.
Electrical route 1.2

f-f-

Final energy consumption

Energy routes

1·7

COMMON

FORMS OF ENERGY

1. Mechanical Energy Mechanical energy is required for movement of objects, changing the shape of the objects, and so on. It is used in transportation, agriculture, handling, processing, and other industrial processes. '

2. Electrical Energy Electrical energy is considered to be the top-grade form of energy. It is used universally as a vehicle of energy. About 30-40% energy distribution in the world is met through electrical supply systems at presento It can be very conveniently and efficiently converted to other forms of energy.

3. Thermal Energy It is used to raise the temperature of an object during industrial processes. It can also be converted to mechanical energy with the help of heat engines. There are three grades of thermal energy:
(a) High Grade (SOO-1000°C and higher)

Fossil fuels, nuclear and hydro resources are considered as conventional sources. Their use has the following advantages and disadvantages.

1.8

ENERGY SOURCES

Advantages
1. Cost At present, these are cheaper than non-conventional sources. The approximate cost of electrical energy derived from different sources at present is given as:

Rs 1.90 per kWh from gas, Rs 1.65 per kWh from coal, Rs 3.0 per kWh from diesel, Re 1.0 per kWh from hydro resource, Rs 1.20 per kWh from nuclear resource. (US$ l~Rs 42.8 as in August 2008)
2. Security As storage is easy and convenient, by storing a certain quantity, the energy availability can be ensured for certain periodo

3. Convenience These sources are very convenient to use as technology for their conversion and their use is universally available.

Disadvantages
1. Fossil fuels generate pollutants. Main pollutants generated in the use of these sources are CO, COz' NO)(' SOx' particulate matter and heat. These pollutants degrade the environment, pose health hazards and cause various other problems. COz is mainly responsible for global warrning. Coal is also a valuable petrochernical and is used as raw material for chernical, pharmaceutical and paint industries. From the long-term point of view, it is desirable to conserve coal for future needs. Safety of nuclear plants is a controversial subject. The major problems with nuclear energy are the following: (a) The waste material generated in nuclear plants has radioactivity quotients of dangerous levels, it remains above the safe limit for a long period of time, and thus is a health hazard. Its safe disposal, which is essential to prevent radioactive pollution, is a challenging task. Also, the disposed radioactive waste is required to be guarded for a long period (till its radioactivity level comes down to a safe limit) lest it goes in wrong hands. (b) There is possibility of accidentalleakage of radio active material from reactor (as happened in Chernobyl, former USSR, in April 1986). (c) Uranium resource, for which the technology presently exists, has a lirnited availability. (d) Sophisticated technology is required for using nuclear resources. Only few countries posses the technology required to use nuclear energy.

2.

3.

1t 8 \ L~

~

Non-conventional Energy Resóurces

Due to these serious disadvantages, Sweden has banned new nuclear plants since 1984 and has planned to dismantle the existing plants in a phased manner. 4. Hydroelectric plants are cleanest but large hydroreservoirs following problems: (a) (b) (c) (d) A large Causes Affects Causes cause the

land area submerges into water leading to deforestation ecological disturbances such as earthquakes wildlife dislocation of a large population and their rehabilitation. SALlENT FI;ATURES OF NON-CONVENTIONAL ENERGY . SOURCES

1·9
Merits 1. 2. 3. 4.

Non-conventional sources are available in nature free of costo They produce no or very little pollution. Thus, by and large, they are environment friendly. They are inexhaustible. They have a low gestation periodo

Demerits 1. 2. 3. 4. In general, the energy is available in dilute form from these sources. Though available freely in nature, the cost of harnessing energy from nonconventional sources is generally high. Availability is uncertain; the energy flow depends on various natural phenomena beyond human control. Difficulty in transporting such forms of energy. ENVIRONMENTAL ASPECTS OF ENERGY

1.10

Environment literally means surroundings. Air, soil and water are the main constituents of environment. Nature has originally provided them to human beings in clean formo However, with passage of time, their quality is continuously being degraded due to various manmade reasons. The chief among them are a number of activities involving energy generation and its utilization. During every energy conversion process, some energy is expelled by the energy conversion system into surroundings in the form of heat. Also, some pollutants may be produced as a by-product of this process. Both of these cause degradation of environment. Every step must be taken to conserve the environment. Therefore, while supplying the increased energy demand, efforts should be made to adopt measures to minimize the degradation of environment. The present trend is to have a trade-off between the two. The future seems to be in favour of developing

Fundamentals

of Energy-Science

and Technology

t.~

~

\

renewable and environment-friendly energy resources. To create public awareness about environment conservation, 5th June is observed as World Environment Dqy.

Ecology deals with the relationship between living organisms (man, animal, plants and vegetation) and the environment. Normally, nature has self-cleaning capability and recycles (renews) its resources thraugh various processes, thus maintaining a state of equilibrium. The water cycle, nitrogen cycle and carbon cycle are the wel1-known examples of this. However, when human interference exceeds naturallimits, the ecological balance gets disturbed.

A greenhouse is an enclosure having transparent glass panes or sheets as shown in Fig. 1.3. It behaves differently for incoming visible (short wave) radiations and outgoing infrared (long wave) radiations. It is transparent for incoming solar radiation, allows entry of sunlight and becomes largely opaque for reflected infrared radiation frorn the earth's surface, thus preventing the exit of heat. Hence, ir maintains a control1ed warmer environment inside for growth of plants in place s where the climate is very cold. The CO2 envelope present around the globe in the atmosphere behaves similar to a glass pane and forms a big global greenhouse. This tends to prevent the escape of heat from the earth, which leads to global warming. This phenomenon is known as greenhouse effect. At present (year 2008), its concentration in the atmosphere Fig. 1.3 Greenhouse is 385 ppm (parts per million) by volume. It is due to this effect that the earth maintains an average surface \emperature of 15°C that is hospitable to life. In the absence of this layer, the earth would be a frozen planet at about -25°C (the temperature of outer atmosphere). However, any further increase in the concentration of CO2 frorn the present level will upset the temperature balance and would cause further warming of the globe, which may have disastrous consequences. Apart from CO2, other harmful gases include methane, nitrous oxide, hydroflourocarbons, sulphur hexafloride and water vapour. All these gases are known as greenhouse gases. The CO2 ernission frorn developed countries accounts for 82% of the total greenhouse gas emission of
Sun

Q t tJ

//////

the world. 1.10.4

Consequences of Global Warming

Global warming is caused mainly due to the ernission of excessive CO2 due to burning of fossil fuels in industry, burning of wood and also due to agricultural practices. This trend is leading to the melting of polar snowcaps, which accounts

Non-conventional Energy Res~urces

for more than 90% of the world's ice, Melting of the polar snowcaps would, in turn, increase the level of oceans and would possibly redefine ocean boundaries inundating low-lying areas and smaller islands. During the last 100 years, the earth's temperature has increased about half a degree Celsius and sea levels have risen 6 to 8 inches (15 to 20 cm). Experts have predicted more frequent and severe heat waves, more intense tropical cyclones, change in rainfall patterns, melting of ice and glaciers at mountains, thus causing floods, followed by decline of water supplies and an increased incidence of vector-borne deceases like malaria. The earth is already showing many signs of worldwide climate change. • Average temperatures have climbed 1.4 degrees Fahrenheit (0.8 degree Celsius) around the world since 1880, much of this in recent decades, according to NASA's Goddard Institute for Space Studies. • The rate of warming is increasing. The 20th century's last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies. And the United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that 11 of the past 12 years are among the dozen warmest since 1850. • The Arctic is feeling the most severe effects. Average temperatures in Alaska, western Canada, and eastern Russia have risen at twice the global average, accorcling to the multinational Arctic Climate Impact Assessment report compiled between 2000 and 2004. • Arctic ice is rapidly disappearing, and the region may have its first completely ice-free summer by 2013. Polar bears and indigenous cultures are already suffering frorn the sea-ice loss. • Glaciers and mountain snows are rapidly melting-for example, Montana's Glacier National Park now has only 27 glaciers, versus 150 in 1910. In the northern hemisphere, thaws also come a week earlier in spring and freezes begin a week later in winter. • Coral reefs, which are highly sensitive to small changes in water temperature, suffered the worst bleaching-or die-off in response to stress-ever recorded in 1998, with some areas seeing bleach rates of 70 per cent. Experts expect these sorts of events to increase in frequency and intensity in the next 50 years as sea temperatures rise. • An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is also attributed in part by some experts to climate change. 1.10.5 Pollution

(a) Indoor Pollution Indoor pollution is mainly caused due to use of conventional chu/has in rural areas. About 5,00,000 children and women die from diseases caused due to indoor air pollution each year_ This requires the need of improved household stoves to reduce indoor pollution.

Fundamentals of Energy-Science and Techno/ogy

L~

~

(b) Outdoor Pollution Outdoor pollution is mainly caused due to use of fossil fuels. Emissions from fossil fuel based plants degrade the environment and cause various other problems. Coal and oil are more pollutant than gas.

Remedy
1. Use of fossil fuels should be slowly curtailed. Less-polluting technologies should be employed for use instead of fossil fuels, i.e., gasified coal, which is less polluting, should be used in power plants. Clean alternative fuels such as hydrogen should be used. Hydrogen is the cleanest fuel and does not cause pollution during power conversion. Electric vehicles or battery-operated vehicles should be used in place of . IC-engine-based vehicles. Various Pollutants and their Harmful Effects The presence of particulate matter

2. CO2 Carbon dioxide is ordinarily not considered a toxic gas. It is essential for photosynthesis and production of essential oxygen and organic matter in nature. But increased concentration of CO2 adversely affects the global climate. Excess emission of CO2 in the atmosphere causes global warming due to greenhouse effect.

Non-conventional Energy Respurces

í

COz in air during the 1940s was less than 312 ppm. During the 1960s it rose to 318 ppm and by 2000 it rose to about 350 ppm. The increasing COz level is mainly due to (a) large-scale combustion of fossil fuels in coal íired thermal power plants all over the world, and (b) felling of trees on a large scale (deforestation) for urbanization, agriculture, and industrialization, resulting in reduced photosynthesis process.

3. co CO is formed due to incomplete burning of carbon in inadequate air. It seriously impairs the oxygen-dependent tissues in the body, particularly the brain, heart and skeletal muscles. CO concentration of 100 ppm causes headache, 500 ppm causes collapse and 1000 ppm is fatal. Smokers inhale CO concentrations of 400 to 450 ppm.
4. SOx The presence of SOz in the air is mainly due to manmade reasons involving combustion of fuels containing sulphur. The contribution from various , sources is as follows:
Power plants Industry Motor vehicles Solid waste disposal Others 70% 15% 8% 5% 2%

SOz can further oxidize to form sulfur trioxide, which in turn forms sulphuric acid when absorbed in water. Harmful Effects (a) Causes respiratory deceases including asthma, and the irritates eyes and respiratory track (b) Causes acid rains, which are harmful to agriculture, forest, vegetation, soil and stones (and thus to buildings) (e) Causes corrosion of metals, deterioration of electrical contacts, paper, textil e, building stones, etc. The safe limit is 80 ug/rrr' (annual average). NOx Oxides of nitrogen such as NzO, NO, NOz' NZ03 are commonly referred as NOx About 80% of nitrogen oxides in the atrnosphere are produced due to natural causes (biological reactions) and about 20% due to manmade causes-mostly due to combustion process in air at high temperature. NOx is formed by the interaction of nitrogen and oxygen at high temperature. Manmade causes include:

Fundamentals

of Energy-Science

and Technology

(a) (b) (c) (d)

Motor vehicles Industry Power plants Solid waste

7% 7% 4% 2%

Harmful Effects

(a) Causes respiratory and cardiovascular illnesses (b) It deprives the body tissues of oxygen (c) It also formsrcid in lungs and, therefore, is more toxic than CO The safe limit is 100 ¡..tg/m3.
1.10.7

Green Power

The term green power is used to describe sources of energy which are considered environmental friendly, non-polluting; and therefore may provide a remedy to the systemic effects of certain forms of pollution and global warming. This is, in fact, the renewable energy sourced from the sun, the wind, water, biomass and waste. Green energy is commonly thought of in the context of electricity, heating, and cogeneration, and is becoming increasingly available. Consumers, businesses, and organizations may purchase green energy in order to support further developñrent, help reduce the environmental impacts associated with conventional electricity generation, and increase their nation's energy independence. Renewable energy certificates (green certificates, or green tags) have been one way for consumers and businesses to support green energy.

ENVIRONMENT-ECONOMY-ENERGY

ANO SUSTAINABLE OEVELOPMENT

Global environmental degradation is one of the most serious threats facing mankind as a result of the expansion of its activities around the globe. One of the international responses to global environmental problemsthe Framework Convention on Climate Change-was ratified and came into effect in March 1994. The convention aims not only at stabilizing CO 2 emissions in developed countries but also at ultimately reducing man-made CO2 emissions globaliy so as to stabilize the global climate. However, with fossil fuels comprising nearly 90 per cent of primary energy sources in the world, the final target of the framework convention seems very ambitious. Environmental degradation cannot be singled out as an independent matter among various global issues. Also important are the interactions among economic development, stable energy supplies, and globe environmental conservation. In the next few decades fossil fuels will continue to be the principal source of energy driving economic development. The source of fossil fuels is stable and their

1.11

~ l' 14 \ L~

Non-conventiona/

Energy Rdources

extraction is affordable. Attempts to restrict the use of fossil fuels for environmental reasons are likely to have a negative impact on economic development and the overall availability of energy. Thus the 'three Es'-enviranment, energy, and economic development are closely interrelated in a complex manner. The strategy for mitigating 'three Es' issues is a strategy for environmentally sustainable economic development. Herman Daly, a famous ecological economist, laid down three conditions for sustainability: 1. The consumption rate of renewable resources is not higher than its recovery rateo 2. The consumption rate of non-renewable resources is not higher than the rate of increase in renewable resource supply. 3. The ernission of pollutants is within the absorption capacity of the environment, Unfortunately, these conditions have been violated for years. Examples of respective violations typically include deforestation, the depletion of fossil fuels, and the increase in COz concentration in the air, Such violations may be hard to reverse in the short term but, unless long-term remedial action is taken, present global development trends will not be sustainable. In particular, a substantial reduction in resource consumption and emissions of pollutants is essential for the development of a sustainable human society on this planet. As evident from the above discussions, economy, environment and energy are closely interrelated and an overall policy is required to deal with them.

At present (year 2008) the annual primary energy consumption of the world is 500 exajoules (equivalent to 138.8 x 1012 kWh of energyor average power of 1.5 x 107 MW). Fossil fuels roughly provide about 90% of this energy and will continue to provide more than 80% of the total energy demand well into the future. Approximately 25% of this energy is consumed in transportation sector and the remaining 75% by industries, domes tic, agriculture-and social consumers. The energy demand has grown astronomically in recent years-with primary energy demand increasing by more than 50% since 1980. This growth is forecast to continue at an annual average rate of 2.2% during 2004-2030. Over 70% of this growth will come from developing countries,

A. Conventional Resources (i) FossiJ Fuels Fossil fuels are so called because these are in fact the fossils of old biologicallife that once existed on the surface of the earth. It is formed in several parts of the earth at varying depths, during several million years by slow decomposition and chemical actions of buried organic matter under favourable pressure, heat and bacterial marine environment. The fossil fuels include coal, oil and gas.
Fossil fuels have been a major source of energy since about 1850, the start of the industrial era. Presently, we are passing through the peak period of the fossil age. As per an estimate, if the world continues to consume fossil fuels at year 2006 rates, the reserves of coal, oil and gas willlast 200,40 and 70 years respectively. This gives only an indication and not a very realistic figure. It is generally accepted that the rate of production of an economic commodity of which a finite quantity exists is governed by the laws of supply and demando As the amount available depletes, the commodity becomes costlier, and its use gradually declines. Also, new reserves are continuously being discovered and new technologies are being invented for those resources which were not considered economical earlier. The locations and estimates of the world's main fossil fuel reserves are indicated in Table 1.3.

Oí) Hydro Resources Among all renewables, hydro power is the most advanced and flexible source of power. It is a well developed and established source of electric power. The early generation of electricity from about 1880, was often derived from hydro turbines. A number of large and medium-sized hydro schemes have been developed. Due to requirement of huge capital investment and strong environmental concerns about large plants, only about one-third of the realistic potential has been tapped so faro Hydro installations and plants are long lasting (turbine life is about 50 years). This is due to continuous steady operation without high temperature or other stresses. Therefore, it often produces electricity at low cost with consequent economic benefits.
The global installed generating capacity of hydro power is about 7,78,038

Mw, which accounts for about 20% of the world's total installed electric powergeneration capacity and about 3% of the world's primary energy supplyí'",
Industrialized countries account broadly for two-thirds and developing countries for one-third of the present hydro power production. Five countries make up more than half of the world's hydro power production: China (100,000 MW), USA (77,350 MW), Canada (71,978 MW), Brazil (71,060 MW) and Russia (45,000 MW). Norway derives 90% of its required electric power from hydro resources. The world's biggest hydroelectric power station is located in Brazil, at Itaipu. Its capacity is 12,000 MW The dam is 7.7 km long and built over the river Pirana.

Oíi) Nuclear Resources U235, U233 (isotopes of uranium) and PU239 (plutonium)
are used as nuclear fuels in nuclear reactors (thermal reactors) and are known as

fissile (orfissionab/e) materia/s. Out of these, only U235 occurs in nature. U233 and PU239
are produced from

"i'h232 (thorium) and U238 respectively in Fast Breeder Reactors

Fundamentals

of Energy-Science and Technology

(FBRs). Th232 and U238are known as fertile materia/s. Natural uranium contains 0.71% of U235and 99.29 % of U238. Uranium reserves in the world are small (expected to last hardly for 59 years at present, i.e., at the 2008 rate of consumption) and its recovery is expensive. Concentrated deposits of uranium are not available. The content of natural uranium in uranium ore is about 0.1-0.5%. Major available sources of uranium are in Australia, Canada, and Kazakhstan and to a lesser extent the USA. There are also a large number of smaller low-grade sites. Thorium reserves are expected to be more than those of uranium. Nuclear power is a least-cost, low-emission technology that can p.rovide baseload power. As on August 2008, there are around 439 nuclear power plants in the world, operating in 31 countries and generating 371,989 Mw, which is about 16% of the world's electricity. France produces 78% of its total electrical power by nuclear means. In the European Union as a whole, nuclear energy provides 30% of the electricity. The nuclear energy policy differs between the European Union countries, and some, such as Austria and Ireland, have no active nuclear power stations. Presently, most commercial reactors are thermal reactors. Fast Breeder Reactors (FBRs) utilize fast neutrons and generate more fissile material than they consume. They generate energy as well as convert fertile material (U238, Th23~ into fissile material (pU239and U233respectively). The breeder technology is not yet commercially developed, the main problem being their slow breeding rate and, therefore, long doubling time (the time required by an FBR to produce sufficient fissile material, to fuel a second id en tical reactor) of around 25 years. With continuing R and D efforts in this direction, it is hoped that by 2050, FBRs will be the main source of power after overcoming the present difficulties. Nuclear fusion reaction has a lot more potential However, controlled fusion reaction has not been by year 2500 some breakthrough will take place in happens, nuclear fusion reaction will be the main and vast resources are available. achieved yet. It is predicted that fusion technology and once this source of energy on the earth.

B. Non-conventional Sources
Non-conventional technologies are presently under the development present, their share is very small. stage. At

(i) Solar Energy Solar energy can be a major source of power and can be utilized by using thermal and photovoltaic conversion systems. The solar radiation received on the surface of the earth on a bright sunny day at noon is approximately 1 kW / rrr', The earth continuously intercepts solar power of 178 billion Mw, which is about 10,000 times the world's demando But so far, it could not be developed on a large scale. According to one estimate, if all the buildings of the world are covered with solar PV panels, it can fulfill electrical power requirements of the

I

Non-conventional Energy Resources

world. Solar PV power is considered an expensive source of power. At present, the capital cost of a solar PV system is Rs 200.00 per W (Rs 20 crore/MW as against Rs 4 crore/MW for coal-fired thermal plant; 1 crore = 10 million).

(íí) Wínd Energy The power available in the winds flowing over the earth surface is estimated to be 1.6 x 107 Mw, which is more than the present energy requirement of the world. Wind power has emerged as the most economical of all renewable energy sources. The installation cost of wind power is Rs 4 crore/ MW(which is comparable to that of conventional thermal plants). There has been remarkable growth of wind-power installation in the world. Wind-power generation is the fastest growing energy source. Wind-power installations worldwide have crossed 94,1 QOMW (at the end of 2007), which is about 1% of the world's electrical power generation capacity. It accounts for approximately 19% of electricity production in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland. Germany is the world leader in wind power with an installed capacity of 22,247 MW (íii) Bíomass Energy Energy resources available from animal and vegetation are called biomass energy resources. This is an important resource for developing countries, especially in rural areas. The principal biomass resources are:
• • • • • Trees (wood, leaves and forest industry waste) Cultivated plants grown for energy Algae and other vegetation from oceans and lakes Urban waste (municipal and industrial waste) Rural waste (agricultural and animal waste, crop residue, etc.)

Solar energy absorbed by plants (through the photosynthesis process) is estimated to be 2 x 1021 J /year. Biomass material may be transformed by chemical or biological processes to produce intermediate bio-fuels such as biogas (methane), producer gas, ethanol and charcoal. At present, there are millions of biogas plants in the world, and most of them are in China.

(ív) Geothermal Energy Geothermal energy is derived from huge amounts of stored thermal energy in the interior of the earth, though its economic recovery on the surface of the earth is not feasible everywhere. Its overall contribution in total energy requirement is negligible. However, it is a very important resource locally. At the end of 2005, the world's total installed electrical power-generating capacity from geothermal resources was about 8,932 MWe and direct thermal-use installed capacity was 28,266 MWt• Globally, use of geothermal power is growing annually at arate of about 3% electrical and 7.5% thermal. The island of Hawaii procures 25% of its electricity from geothermal resources. Likewise, geothermal electrical energy production in El Salvador is 23% of the country's total installed electricity-generation capacity. The oldest geothermal power generator is located

Fundamenta/s

of Energy-Science

and Technoíogy

LU
1

~

at Lordarello in Italy, commissioned of power.

in 1904 and presently producing 460 MW

(v) Ocean Tidal Energy Tidal energy is a form of hydro power that converts energy of ocean tides into electricity or other useful forms of power. It is in the developing stage and although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. There are at present only a few operational tidal power plants. The first and the biggest, a 240-MW tidal power plant was built in 1966 in France at the mouth of the La Rance river, near StoMalo on the Brittany coast. A 20-MW tidal plant is located at Nova Scotia, Canada, and a 400-kW capacity plant is located at Kislaya Guba, near Murmansk, Russia, on the Barents Sea. Many sites have been identified in USA, Argentina, Europe, India and China for development of tidal power. (vi) Ocean Wave Energy Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work. Good wave power locations have a flux of about 50 kilowatts per metre ofshoreline. As per an estimate, the potential for shoreline-based wave power generation is about 50,000 MW Deep-water wave-power resources are truly enormous, but perhaps impractical to capture. Some wave plants are recently deployed at few places. The world's first 2250-Mw, commercial wave farm is based in Portugal. Other plans for wave farms indude a 3 MW plant in the Orkneys, off northern Scotland, and the 20MW wave-hub development off the north coast of Cornwall, England. (vii) Ocean Thermal Energy Conversion OTEC technology is still in its infant stages. Conceptual designs of small OTEC plants have been finalized. Their commercial prospects are quite uncertain. The potential is likely to be more than that of tidal or wave energy.

1.14

ENERGY SCENARIO IN INDIA

India is both a major energy producer and consumer. India currently ranks as the world's eleventh greatest energy producer, accounting for about 2.4% of the world's total annual energy production, and as the world's sixth greatest energy consumer, accounting for 3.3% of the world's total annual energy consumption. Thus, India is a net energy importer, mostly due the large imbalance between oil production and consumption. As per 2005 data for India, the total annual primary energy production and consumption was 11.73 Quad. BTU and 16.205 Quad. BTU respectively. The per capita primary energy consumption is 520 KGOE for India, whereas the world average is 2366 KGOE (2007 data). Similarly, the per capita annual electrical energy consumption in India is 702 kWh whereas the world average is 2600 kWh (2007 data).

Electrical Power Generation The present total installed capacity of electrical power generation in India is 1,44,912 MW (as on June 30, 2008), produced from various resources as given in Table 1.5.
Table 1.5

A. Conventional (i) Fossil Fuel India has vast teserves of coal, the fourth largest in the world after the USA, Russia and China. According to a rough estimate, the total recoverable coal in India is 90 billion tonne, about 10% of the world's total. With the present rate of consumption, India will have enough coal for about 300 years. Indian coal has high ash content (25-50%), low heat value (3000-4000 kcal/kg) and low sulphur content (1%). We have only 0.6% of the world's oil and gas reserves. Oil and gas represent over 40 per cent of the total energy consumption in India. About 35% of oil needs are met through domestic production and the balance 65% thraugh imports. Crude oil reserves are estimated as 600 million tonrte, enough to last about 22 years at the present rate, if no further discovery is made. Natural gas reserves are estimated as 1000 billion m", enaugh to last for

1\
Fundamenta/s of Energy-Science and Technology

C-.-~

30 years, if no further discovery is made. Oil and gas reserves are insufficient even for the transportation sector. The domestic production is decreasing slowly, However, recent findings of gas reserves in Rajasthan and the Krishna-Godavari basin off the Vishakhapatnam coast may change the trend. The actual impact will be known once these resources are fully developed and production begins.

(ií) Hydro Resources India stands seventh in the list of nations with hydro resources with a total potential of 100,000 MW of which approximately 36,033 MW has been developed. Huge installation cost, environmental and social problems are major difficulties in its development. (iii) Nuclear Resources India has modest reserves of uranium, mostly located at Jadugoda, Jharkhand. Out of the total electrical power generation, 2.8% is being generated by nuclear means. uclear-power generation is planned to reach 10,280 MW by the year 2012 and 20,000 MW by 2020.
Thorium is available in abundance in India in the form of monazite (ore) in the sand beaches of Kerala. The economically viable reserve of thorium in India is estimated at 3,00,000 tonnes, which is 25% of the world's thorium reserves. Thorium is a fertile material, which is converted into a fissionable material U233 in an FBR. The U233 so obtained may be used in a normal thermal reactor such as PHWR. For the development of the nuclear energy technology, a research facility IGCAR (Indira Gandhi Centre for Atomic Research) has be en established in 1971 at Kalpakk.am, Tamil Nadu. The founder of the country's atomic energy program Bhabha outlined a three-stage program as far back as 1955. Dr Homi Je~angir

Stage 1 In the first stage, Pressurized Heavy Water Reactors (PHWRs) using natural uranium (0.7% U235 and 99.23% U23s:l as fuel and heavy water both as coolant as well as moderator, would be set up. A PHWR is a thermal reactor that consumes only the U235 part of the natural uranium and U238 is mostly left in spent fuel. Stage 2 The second stage envisages the construction of FBRs, which will use spent fuel (depleted uranium) of the PHWRs, i.e., U238 and convert it to a fissionable material, plutoniumé". The plutonium+", thus obtained, will be used as fuel in a thermal reactor. Stage 3 In the third stage, thoriurrr'" will be converted to U233 in a fast breeder
reactor. The U233 will then be used as fuel in a thermal reactor. The energy generated in the second stage is 60 times more than that available from PHWR by the same amount of natural uranium, as in this stage the uranium is fuliy utilized. However, in the first stage, only the U235 part, which accounts for 0.7% in the natural uranium, is utilized.

t

Non-convennoncl Energy Resources

India has mastered the technology of the first stage with 15 commercial PHWRs plants (located at Narora, Rawatbhatta, Kakrapar, Kaiga, Kalpakkam, Kodamulam and Trombay) functioning in the country to date. However, natural uranium reserves are enough to generate only 12,000 MWe from PHWRs. But with FBRs that use plutonium, we can generate 3,50,000 MWe, which is a massive amount. The Stage 2 reactor at Kalpakkam (in FBTR, 'Fast Breeder Test Reactor') attained criticality in 1985. It is fully operational and feeding 1 MW power into the Tamil Nadu grid. However, certain technological difficulties are yet to be overcome. Construction work for a more advanced 500 MWe Prototype Fast Breeder Reactor (PFBR) has begun from 2002 at Kalpakkam and it is expected to reach criticality in 2009. R and D work on a Stage 3 reactor, ('Karnini reactor'), which will utilize thorium is also going on at IGCAR, Kalpakkam.

B.

Non-conventional

Located in the tropical region, India is endowed with abundant renewable energy resources, i.e., solar, wind and biomass including agricultural residue which are perennial in nature. Harnessing these re source s is best suited to meet the energy requirement in rural areas in a decentralized manner. India has the potential of generating more than 1,00,000 MW from non-conventional resources. Up to June 30, 2008, the electrical power generation by non-conventional resources has reached 12,194 Mw, which is about 8.4% of total installed electrical powergeneration capacity. The government plans to increase this share to 10% by 2012. The current status (as on 31.12.2007) of various resources are given in Table 1.6: rabie 1.6
Renewable energy-estimated (Dec. S.N. 1. 2.
2007

(i) Wind Energy The highly successful wind power programme in India was initiated in 1983-84 and is entirely market driven. This sector has been growing at over 35% in the last three years. India currently (year 2008) stands fourth in the world among countries having installed large capacity wind generators, after Germany, USA and Spain. The current (Iuly 2008) installed capacity for wind power stands at 8,696 MW, and is mostly located in Tamil Nadu, Gujarat, Maharashtra and Rajasthan. The government aims to add 10,000 MW from wind during XIth plan period (2007-2012).
(ii) Solar Energy India receives a solar energy equivalent of more than 5,000 trillion kWh per year, which is far more than its total annual consumption. The daily global radiation is around 5 kWh per sq. m per day with sunshine ranging between 2300 and 3200 hours per year in most parts of India. Though the energy density is low and the availability is not continuous, it has now become possible to harness this abundantly available energy very reliably for many purposes by converting ir to usable heat or through direct generation of electricity. The

Non-conventionaJ

Energy Re"sources

I

conversion systems are modular in nature and can be appropriately decentralized applications.

used for

Solar Thermal Energy Programme Use of solar thermal energy is being promoted for water heating, cooking, drying and space heating through various schemes. The government is proposing to make solar-assisted water heating mandatory in certain categories of buildings through amendments in the building bylaws. Bangalore has been declared a solar thermal city with special attention to popularize solar water heaters, and Thane in Mumbai is to fol1ow soon. Several large projects are under consideration at the Ministry of New and Renewable Energy Sources. India is planning on developing 60 'Solar Cities' based on a model already practiced in New York, Tokyo and London. The target is to reduce the use of the conventional energy resources by at least 10% over the next five years. Recently, the idea of an Integrated Solar City with ambitious 5 GW solar projects has been mooted by The Clinton Foundation for Gujarat. Solar Photovoltaic Programme Solar PV energy is being used for solar lanterns, home-lighting systems, street lighting systems, solar water pumps and power plants. A number of 100-kW grid interactive plants are already in operation at various place s in the country. A 200 kW plant is instal1ed recently at the native village of Sardar Bhagat Singh (Village Khatkar Kalan, Dt. Nawanshahar, Punjab).

is promoting the establishment of special sales outlets under the name Aditya Solar Shops in major cities (104 cities so far). Different models of solar-system devices from various manufacturers are sold through these shops in order to provide the customer a wide choice.
Aditya (iii) Biomass Energy A large quantity of biomass is available in our country in the form of dry waste like agro residues, fuel wood, twigs, etc., and wet wastes like cattle dung, organic effluents, sugarcane bagasse, banana stems, etc. The potential for generation of electric power/ cogeneration is 16,881 MW from agro residues and 5000 MW from bagasse through cogeneration. The potential from urban waste is 2,700 MW Also, there is a vast scope for produccion of bio-diesel from some plants. These plants require little care, can be grown on fallow land and can survive in harsh climatic conditions. Energy farming may be adopted in marginal and infertile lands of the country. (iv) Small Hydro Resources Hydro resources of capacity less than 25 MW are called small, less than 1 MW are called mini and less than 100 kWare called micro hydro resources. The total potential is 15,000 MW out of which 2,015 MW has been realized by approximately 611 plants. (v) Geothermal Energy The potencial in geothermal resources in the country is 10,000 MW As a result of various resource assessment studies/surveys, nearly 340 potential hot springs have been identified throughout the country. Most of

Solar Shops The ministry

Fundamentals

of Energy-Science

and Technology

tu

~

them are low-temperature hot-water resources and can best be utilized for direct thermal applications. Only some of them can be considered suitable for electrical power generation. The geothermal reservoirs suitable for power generation have been located at Tattapani in Chhattisgarh and Puga valley of Ladakh, Jammu and Kashmir. A 300 kW demonstration electric-power-production plant is being installed at Tattapani. Hot-water resources are located at Badrinath, Kedarnath and a few other locations in the Himalayan ranges and elsewhere. They are being used mostly for heating purposes and very little has been developed.
(vi) Ocean Tidal Energy There is no functional tidal plant at present and the total potential has been estimated as 9,000 MW Three sites have been identified for development of tidal energy.

The Ministry of Non-conventional Energy Sources has sponsored the preparation of a feasibility report by the West Bengal Renewable Energy Development Agency (WBREDA) to set up a 3.6 MW capacity demonstration tidal power plant at Durgaduani Creek in the Sunderbans area of West Bengal.
(vii) Ocean Wave and OTEe Resources A 150-kW pilot plant has been installed at Vizhingum harbour near Thiruvananthapuram, Kerala. The average potential (annual basis) for Indian coasts has been estimated at around 0.02 MW 1m of wavefront. There is a proposal for an OTEC plant at the Minicoy island of Lakhshdweep.

Emerging technologies like 'fuel cell' and 'hydrogen energy' are suited for stationary and portable power generation, which suits transportation purposes. In view of the growing importance of fuel cells and hydrogen, a National Hydrogen Energy Board has been created. The board will provide guidance for the preparation and implementation of the National Hydrogen Energy Road Map, covering all aspects of hydrogen energy starting from production, storage, delivery, applications, safety issues, codes and standards, public awareness and capacity building. Eco-friendly electric vehicles for transportation are being field tested for improving their performance.

Energy is a critical building block for the development of the economy of a country. It is considered as a GDP multiplier. India is the sixth largest energy consumer in the world. To deliver sustained growth rate of 8-9% through the next 25 years till 2031-32, India needs to increase its primary energy supply 3-4 times and its electricity generation capacity about 6 times.

;
Non-conventional Energy Resources

Electricity is an essential requirement for all facets of our life and ir has been recognized as a basic human need. It is the key to accelerating economic growth, generation of employment, elimination of poverty and growth of human development especially in rural ateas. lndia's electric power sector has shown an annual growth rate of 5.1% during the last three years of the Xth 5-year plan. The demand for electric power is increasing at about 9%. Consequently, the supply-demand gap has been widening, resulting in an average annual peak shortfall of about 16%. This has resulted in load-shedding, under-frequency tripping, large blackouts and equipment failures. The installed capacity of electric-power generation has grown from 1,362 MW in 1947 to 1,44,564 MW as on jüne, 30, 2008 (Refer [35,36] for current updates). The capacity utilization is estimated as less than 60%. The energy planning during the past few 5-year plans is given in the following Table 1.7.
Table 1.7 Energy planning during the past few 5-year plans[34dS] Demand 52,000MW 75,000MW 1,05,000MW 1,32,000MW 1,46,OOOMW 2,05,000MW Installed capacity 47,000MW 65,000MW 85,000MW 1,10,000 MW 1,24,569 MW Shorlage 5,000MW 10,000MW 20,000MW 22,000MW 21,431 MW

To bridge the déficits and cater to future demands, the country needs an additional power generation capacity of approximately 100,000 MW over the next few years. The national goal of electrical power generation by 2012 is 2,00,000 MW in order to ensure reliable and quality power to all citizens. Out of this, about 10,000 MW will be sourced from non-conventional sources. The per capita energy consumption is targeted as 1000 kWh by 2012 against the present (year 2008) level of 702 kWh. The growth in per capita electrical energy consumption and the growth projections of the power sector are given in Table 1.8 and Table 1.9 respectively.
Table 1.8 Year Per capita annual energy consumption
(kWh)

The present (year 2008) household access to electricity is 56% and the rural household coverage is 44%. Electrification of rural areas is very important for a uniform development of the country. There are about 6 lakh villages in the country, and an estimated 80,000 villages are still to be electrified. Of these, there are about 20,000 villages in remote and difficult areas, which are unlikely to be electriíied by conventional grid extension. Most of these villages are in hills, forests, deserts and islands. The government aims to electrify all the remaining unelectrified villages in the country in a timebound manner through special electrification prograrnmes. The remote villages and hamlets are to be electriíied through decentralized generation using non-conventional energy sources such as solar energy, biomass and rnicro/mini/small hydro resources. The government aims to electrify all such villages by the year 2007 and all households by 2012. The technology to be used will depend upon the size of the village and the resources available locally. APPlIED THERMODYNAMICS-A REVIEW

Thermodynarnics is an axiomatic science which deals with the relation between heat, work and properties of a system which are in equilibrium. It describes the state and the change in state of physical systems. Thermodynarnics basically entails four laws or axioms, known as the zeroth, first, second and third law of thermodynarnics. • The zeroth law deals with thermal equilibrium and establishes the concept of temperature. • The first law throws light on the concept of internal energy. • The second law indicates the lirnit of converting heat into work and introduces the principle of increase of entropy. • The third law defines the absolute zero of entropy

1.15

Surroundings (environment)

System A system is the finite quantity of matter or a prescribed regíon of space. Boundary enclosing a system. The surroundings The actual or a hypothetical envelope system is known as the boundary of the boundary may be fixed or variable. The are external to the system.

Fig. 1.5 A system

Non-conventíona/

Energy Rdources

•

Closed System If the boundary of a system is impervious to the flow of matter, it is called a closed system. Open System An open system is one in which matter flows into or out of the system. Most of the engineering systems are open systems. Isolated System A system that exchanges neither energy nor matter with any other system or with the errvironment is known as an isolated system. Adiabatic System An adiabatic system is one which is thermally insulated from its surroundings, i.e., it does not exchange heat with its surroundings. It can, however, exchange work with its surroundings. If it does not, it becomes an isolated system. Isothermal System An isotherrnal

system

lS

one which maintains

constant

temperature.
Intensive Property Intensive property is that property which does not depend on the mass of the system, e.g., pressure or temperature. Extensive Property Extensive property is related with the mass of a system, e.g., volume or energy. Phase A phase is that quantity of matter which is homogeneous chernical composition and physical structure.

throughout in

Homogeneous System A system which consists of a single phase is termed a homogeneous system. Examples are a mixture having air plus water vapour, water plus nitric acid or hydrogen plus methane. Heterogeneous System A system which consists of two or more phases is called a heterogeneous system. Examples are, a mixture of water plus oil, water plus steam and ice plus water.
State

Each unique condition of the system is known as a state. Process A process occurs when a system undergoes a change in state or an energy transfer at a steady state. A process is illustrated by a curve on a P- V (pressurevolume) diagram or a T-S (abs. temperature-entropy) diagram. A process has a certain path between the starting point and the end point. A process begins with a certain state and ends with certain state of working fluido

p

Fig. 1.6 A process
and cycle

Cyc/e Any process, or series of processes, whose end states are identical is termed as a cycle.

Fundamentals

of Energy-Science and Techno/ogy

Irreversible Process An irreversible process does not trace the same path when reversed. The irreversibility may be due to • friction • heat flow (always from hot to cold) • mixing of two different fluids in different states Thermal Equilibrium In thermal equilibrium, the temperature at all points of the system and it does not change with time. will be the same

Mechanica/ Equilibrium In mechanical eguilibrium, there are no unbalanced force s within the system. The pressure in the system is same at all points and does not change with time. Chemica/ Equilibrium In chernical eguilibrium, no chernical reaction takes place in the system and the chemical composition which is same throughout the system does not vary with time. Thermodynamic Equilibrium achieved the A system is in thermodynarnic eguilibrium if it has

• thermal equilibrium, • mechanical eguilibrium, and the • chernical eguilibrium states. Quasi-static Process Quasi means 'almost'. A quasi-static process is also called a reversible process. This process is a succession of eguilibrium states and portrays infinite slowness in its characteristic features. Specific Heat The specific heat of a solid is usually defined as the heat required to raise the temperature of unit mass of the solid through one degree. For a solid of mass m and specific heat e, the heat dQ reguired to increase the temperature by d T: . .

For a perfect gas it is assumed that u = Owhen T = O,hence K is zero. Thus, the internal energy of 1 kg of a perfect gas,

u=eTv

Fundamentals of Energy-Science and Technology

Internal energy for a perfect gas of mass m is

U=mcT

v

Therefore, for a perfect gas, gains of internal energy in any process (reversible or irreversible) between two states 1 and 2 is

(1.2)
Enthalpy, h is defined as the sum of internal energy, u, and the pressure-volume product,pv:

Enthalpy

h=u+pv

(1.3)

The enthalpy of a fluid is the property of the fluid since it consists of the sum of a property and the product of two properties. Since enthalpy is a property, it can he introduced into both flow as well as non-flow processes. Total enthalpy of mass, m of a fluid can be given as

H=mh=

U+pV

(1.4)

For a perfect gas, rewriting Eq. (1.3),

h

= u + pv
= e T+ RT = (e + R)T
v
v

h = ep T
andH=

[from Eq. (1.1)]

(1.5)
(1.6)

mep T

(Note that since u has to be zero at T = 0, therefore, h =

°

at T = O.)

1.15.3 First law of Thermodynamics
In the early part of the nineteenth century, scientists discovered the concept of energy and the hypothesis that 'energy can neither be created nor destroyed , which carne to be known as the law of conservation of energy. The first law of thermodynamics is merely one statement of this generallaw with particular reference to heat energy and mechanical energy, i.e., work. The first law of thermodynamics can be stated as, 'when a system undergoes a thermocjynamic cyclethen the net beat supplied to the systei»jrom the surroundings is equal to the net work done I?Jthe syste»: on its surroundings.' or

fdQ=fdW

L~

l' 32

1\
\ Non-conventional Energy ~esources

where

f

represents the sum for a complete cycle.

Performance of Heat Engine and Reverse Heat Engine In Pig_ 1.7, a heat engine is used to produce maximum work from a given positive heat transfer, The measure of success is called the thermal efficien0' of the engine and is defined by the ratio

11th

=

W Q¡ W = net work transfer from engine Q¡

(1.7)

where

= heat

transfer to the engine

Por a reversed heat engine acting as a refrigerator, when the purpose is to achieve the maximum heat transfer from the cold reservoir, the measure of \ success is called the coefficient of performance (COP)_ It is deíined by the ratio

(COP)
where

refrigerator

=& W

(1_8)

Qz

= heat transfer from the cold reservoir W = the net wok transfer to the refrigerator

Por the reversed heat engine acting as a heat pump, when the purpose is to achieve maximum heat transfer to a hot reservoir, the measure of success is again called the coefficient of performance (COP)_ It is defined by the ratio

(COP)
where

hcat

pump= & W
to the hot reservoir transfer to heat pump

(1.9)

Q¡

= heat transfer W = the net work

In all the above three cases, the application of the first law gives the relation

Q¡-Qz = W, and this can be used to rewrite the expressions for efficiency and COP solely in terms of heat transfers:
llth

=

Q¡ -Qz Ql

(1.10) (1.11)
2

(COP)

refrigerator

= QlQzQ -

(COP)heatpump

(1.12)

1\.
Fundamentals

of Energy-Science
fri re gerator

and Technology

~3U

It may be seen that values of 'Ilthand (COP) while (COP)heatpumpis lways greater than unity. a
Hol reservoir

are always less than unity,

Hol reservoir

O,

O, = O2+W
__ W

Heat engine

f---

Healpump Or refrigealor

O2

Q2

Cold reservoir

Cold reservoir

(a) Heal engine

(b) Heat pump or refrigerator

Fig.l.7

Heat and work flow in a heat engine and reversed heat engine

1.15.4

Second Law of Thermodynamics let us highlight the

Before discussing the second law of thermodynamics, shortcomings of the first law of thermodynamics. Limitations

of The

First Law

of Thermodynamics

• It has been observed that energy can flow from a system in the form of heat or work. The first law of thermodynamics sets no limit to the amount of the total energy of the system which can be caused to flow as work. A limit is imposed, however, as a result of the principIe enunciated in the second law of thermodynamics which states that heat will flow naturally from one energy reservoir at a higher temperature to another at a lower temperature, but not in the opposite direction, without assistance. • The first law of thermodynamics establishes equivalence between the quantity of heat used and the mechanical work but does not specify the conditions under which conversion of heat into work is possible, neither the direction in which heat transfer can take place. This gap has been bridged by the second law of thermodynamics. There are two classical statements of the second law of thermodynamics, known as Kelvin-Planck statement and Clausius statement.
Kelvin-Planck Statement It is impossible to construct an engine, which while operating in a cycle produces no other effect except to extract heat from a single reservoir and do equivalent amount of work.

Non-conventiona/

Energy fesources

•

Clausius Statement It is impossible for a self-acting machine working in a cyclic process unaided by any external agency, to convey heat from a body at a lower temperature to a body at a higher temperature_

Entropy Entropy is an extensive property of a substance and is designated by S. It may be defined for a reversible process in accordance with the relation:
d5 _ or

(OQ)
T
rev

Incremental

entropy

= ratio

of heat change and absolute temperature.

In simple terms, it is heat (in joules) per Kelvin. For a reversible process, if SI and 52 are the respective entropies at the initial and final states then the change in entropy depends on the initial and final state only, and not on the path followed by the process. It is therefore a property. Thus, change in entropy when the system undergoes a reversible change from State 1 to State 2 is

SI-

52

= T

2(OQ)

!

rev

Critical point

,
.~ Liquid ~ phase ~ Boiling o--1o-rviPa------/
ó' s: "'~

'\ Condensation,'

% phase
/

Vapour

c3'

~

~

~ 0'/

Isentropic Process An isentropic process is one during which the entropy of the system remains constant. It can be proved that any reversible adiabatic process is anisentropic process. Temperature-entropy Diagram

------------~------------ e B 1 MPa
Liquid plus vapour phase

for apure substance The A thermodynamic properties of a substance are often shown on Entrcpy, S a temperature-entropy (T-S) diagram, shown in Fig. 1.8. The Fig.1.8 Temperature - entropy diagram for steam general features of such diagrams are the same for all pure substances. These diagrams are important because they enable us to visualize the changes of state that occur in various processes.

Carnot cycle The Carnot cycle, which works on reversible cycle was suggested by the French engineer Sadi Carnot in 1824. Any fluid may be used to operate the Carnot cycle, which is performed in a cylinder as shown in Fig. 1.9(a). Heat is caused to flow into the cylinder by the application of heat from a high-energy source to the cylinder head during expansion, and to flow from the cylinder by the application of a low-temperature energy source to the head during compression.

Fundamentals

of Energy-Science and Technology

The following are the four stages of a Carnot cycle: Stage 1: (Process 1-2) Hot energy source is applied. HeatQ¡ is taken in and the fluid expands isothermally and reversibly at constant temperature TI' Stage 2: (Process 2-3) The cylinder becomes a perfect insulator so that no heat flow takes place. The fluid expands adiabatically and reversibly whilst temperature falls from TI to T2. Therefore, the process is an isentropic one. Stage 3: (Process 3-4) Cold energy source (sink) is applied. HeatQ2 flows from the fluid and it is compres sed isothermally and reversibly at a constant lower temperature, T2• Stage 4: (Process 4-1) The cylinder head becomes a perfect insulator so that no heat flow occurs. The compression is continued adiabatically and reversibly during which temperature is raised from T2 to TI' The work delivered by the system during the cycle is represented by the enclosed area of the cycle. Again, for a closed cycle, according to the first law of thermodynamics, the work obtained is equal to the difference between the heatQI supplied by the source and the heatQ2 rejected to the sink.

The thermal efficiency,

'Ilth

Work output Heat supplied by the source
'Il

Area under curve 1- 2 -3 - 4 Area under curve 1- 2- 3'-4'

Q¡ - Q2
Q¡ (1.13)

th

=1--

T2 T.
I

The Carnot cycle is an ideal condition requiring a reversible heat engine and cannot be performed in practice because of the following reasons. • It is impossible to perform a frictionless (i.e., reversible) process. • It is impossible to transfer heat without a temperature gradient. • An isothermal process can be achieved only if the piston moves very slowly to allow some time for heat transfer so that the temperature remains constant. An adiabatic process requires the piston to move as fast as possible so that the heat transfer is negligible due to a short interval of time available. The adiabatic and isothermal processes take place during the same stroke, requiring the piston to move very slowly for the initial part of the stroke and very fast for the remaining part of the stroke. This extreme variation of motion of the piston during the same stroke is not possible.

~3U

1\

Non-conventiona/

Energ~ Resources

Though it is not a practical engine cycle, the conceptual value of the Carnot cycle is that it establishes the maximum possible efficiency for an engine cycle operating between TI and Tz- The Carnot cycle can be thought of as the most efficient heat engine cycle allowed by physical laws. When the second law of thermodynamics states that not all the supplied heat in a heat engine can be used to do work, the Carnot efficiency sets the limiting value on the fraction of the heat which can be so used.
I-Piston

Therefore, Source 2 will provide larger amount of power (even though its efficiency is lower).
Rankine Cyde The rankine cycle is a vapour-power cycle on the basis of wh.ich a steam turbine (or engine) works. The various components and the processes involved in a Rankine cycle are shown in Fig. 1.10(a). It cornprises of the following processes:

Process 1-2 Reversible adiabatic expansion in the turbine (or steam engine) to produce output work Wr Process 2-3 Constant pressure transfer of heat in the condenser. Steam is condensed to water and heatQz is removed. Process 3-4 Reversible adiabatic pumping process, where the system accepts some work W as input. However, this work is negligible compared to work output of the turbine, especially when the boiler pressure is low.

Fundamentals of Energy-Science and Technology

Process 4-1 Constant pressure transfer of heatQ1 in the boiler. Thermodynamic changes during the Rankine cycle are shown on P- V and

T-S diagrams given in Fig. 1.10 (b, c). The area under the closed loop 1-2-3-4
represents the net work output. The efficiency of a Rankine cycle can be written as (h 1- h 2 )-(h h1-h4 Usually, the pumping power is very small as compared to power produced by a turbine, WT > > Wp
J: Th erelore, '"
"IRankine 4-

h 3)

. '"

h¡-h2 _ h - h
1 4

(1.14)

Cooling water ..•. Q2

(a)

I
I

r,

\
\

4
I "
\

P1

" -,
"
\

,
Superheated steam
I

..•..

/

-- ...• -,
\ \ \

\ \ \ \

2

2

v
(b) (e)

s
Fig.1.10

Rankine cycle

Effects of Operating Conditions on Rankine Cycle Efficiency
Rankine cycle efficiency can be improved by • increasing the temperature at which steam is supplied to the turbine • decreasing the temperature at which steam is rejected by the turbine

,
r

1f 40 \
L ~

~

Non-conventional Energy Resources

This can be achieved by making suitable changes in the conditions of the boiler and condenser.
1. Increasing Boiler Pressure It has been observed that by increasing the boiler pressure (other factors remaining the same), the efficiency rises first and then drops after reaching its peak value (of about 35-45%) at about 166 bar. 2. Superheating the Steam If the steam is superheated before it enters the turbine, the efficiency of the Rankine cycle increases, other factors remaining the same. This also increases the life of the turbine blades due to absence of water particles.

3. Reducing the Condenser Pressure By reducing the condenser pressure, the temperature at which heat is rejected can be reduced, thus increasing the thermal efficiency of the cycle. However, this would also increase the cost of condensation apparatus.

The efficiency of the Rankine cycle is also improved methods. (a) (b) (c) (d) regenerative feed heating reheating of steam water extraction using binary vapour

Brayton Cycle The Brayton cycle is a gas-power cycle on the basis of which a thermodynamic device (engine or turbine) works to produce mechanical power. The various components and the processes involved in a Brayton cycle are shown in Fig. 1.11 (a). It uses air as a working fluid and works at temperatures wel1 in excess of 500°C. The expansion and compression processes are reversible and adiabatic while heat addition and rejection takes place at constant pressure. The hot compressed gas is allowed to expand through a turbine performing work. The exhaust gas from the turbine is fed to a heat exchanger where the heat is rejected and then compressed by the compres sor to complete the cycle. It comprises of the following processes: Process 4-1 Reversible adiabatic (i.e., isentropic) compression. Here, a work Wc is accepted by the system as input. Process
1-2

Constant pressure transfer of heatQl in the combustor. expansion in the turbine. A work WT is

Process 2-3 Reversible adiabatic produced.

Fundamentals

of Energy-Science

and Technology

Process 3-4 Constant
I

pressure heat OUtputQ2 by the condenser.

Thermodyna1c changes during the Brayton cycle are shown on P- V and Y-S cliagrams given in Fig. 1.11 (b, c). The area under the closed loop 1-2-3-4 represents the net work output (Wy-W). The performance of a Brayton cycle can be improved by inserting a regenerator between the turbine exhaust and the cooler for preheating the compres sed gas prior to the combustor. The efficiency of a Brayton cycle can be written as 1 1]Bra)"oo =1-~ (1.15)

r,

where

rk

is the compression

ratio (;:)

and y is the ratio of the two specific

heats. In terms of pressure ratios rp;
'Y\ • J

Brayron

-

-

1-----:---::-:-(y-l)/y
rp

1

(1.16)

In a Brayton cycle, the work input during compression is a significant amount as the working fl.uid is gas. The compres sor consumes roughly 50% of the power produced by the turbine, reducingthe overall efficiency of the cycle. This is in contrast to a Rankine cycle where pumping power is negligible as the working fl.uid is in liquid form (which is uncompressible) during the compression (pumping) process. Typical data for a Brayton cycle based gas turbine (coal fired): Inlet temperature 540°C -1425°C Inlet pressure ;:::; 0 atm 3 Efficiency ;:::26%-39%

=

Worl< out, WT Compressor 4 3

Heatout, Q2
(a) (b)

V
(e)

s

Fig. 1.11 Brayton cycle

Stirling Cyc1e The Stirling cycle is similar to a Carnot cycle, except that two acliabatic processes are replaced by two constant volume processes. A suitable gas or air is used as working fluido The system components are shown in Fig. 1.12(a). The heat adclition and rejection takes place at constant temperatures. The cycle comprises of the following processes:

L~

,.

1\

42 \ Non-conventional Energ~Resources

Process 4-1 The working fluid receives heat at constant volume in a regenerative heat exchanger from the exhaust fluid returning from the turbine. Process 1-2 In this process, the working fluid receives heat at constant (high) temperature and expands in a turbine producing WT output. Process 2-3 The working fluid loses heat at constant incorning to the turbine. Process 3-4 The working fluid is compressed and heatQz is rejected to the ambient. volume to the fluid

at constant

(low) temperature

The heat transfer in a r~generative heat exchanger by a matrix of wire gauze or small tubes. The main lies in making an efficient regenerator of reasonable a temperature comparable to that used in internal efficiency of a Stirling cycle is given as
l']Stirling

is accomplished reversibly difficulty in a Stirling cycle size which can operate at combustion engines. The

The performance of various thermodynarnic cycles can be compared qualitatively on a T-S diagram shown in Fig. 1.13. These diagrams are not drawn on a common scale and only their shapes are compared. The temperature, pressure and entropy ranges are different for different cycles. As seen from this figure, the Carnot cycle is represented by a rectangle and produces maximum output. The Stirling cycle produces the next maximum in the remaining three cycles. The main

Fundamentals of Energy-Science

and Technology

t.U

1\

lirnitation however, is the design of a suitable, efficient regenerator, especially in large sizes. Also, the Stirling cycle is not preferred in large power plants due to many other practical problems. The Rankine cycle is generally preferred and is widely used due to its superior overall cycle efficiency and component sizes.

~Ifc.m°' i~ ""j VR'
~ S -3 S Fig.1.13 Comparison 2

s of power
cye/es

s

How is per capita energy consumption related with standard of living? Comment on the oil crisis of 1973. 3. What are primary and secondary energy sources? 4. What are conventional and non-conventional energy sources? 5. List various non-conventional energy resources. Give their availability, relative merits and their classification. (UPTU Lucknow 2005-06) 6. Discuss the main features of various types of renewable and non-renewable energy sources and explain the importance of non-conventional energy sources in the context of global warming. (UPTU Lucknow 2007-08) 7. What is meant by renewable energy sources? 8. What do you understand by commercial energy? 9. What are the advantages and limitations of non-conventional energy sources? 10. What is the percentage share of fossil fuels in the total energy consumption of the world? 11. What percentage of energy requirement is met by coal in India? 12. Discuss the main feature of non-conventional energy sources. (UPTU Lucknow 2003-04) 13. Discuss different renewable sources of energy with special reference to the Indian contexto (UPTU Lucknow 2003-04) 14. What do you understand by energy chain? 15. What are the advantages and disadvantages of conventional energy sources? 16. What do you understand by greenhouse effect and what are its consequences? How is it caused? 17. What are greenhouse gases? 18. What do you understand by green power? 19. Which is the cleanest of all fuels and what is its heating value? 20. Indicate the heating values of bituminous coal, coke, peat, diesel, propane and natural uranium. 21. What is the present annual primary energy consumption of the world? At what rate is it growing? 22. Comment on the future availability trend of fossil fuels in theworld.
1.

2.

• Non-conventionc 1 Energyi fesources

~3. What is the present world hydro-power potential and how much has been tapped so far? 24. Which country relies the most on nuclear energy for its energy requirements? 25. What is the present status of nuclear energy and what are its future prospects? 26. What is the potential in solar energy the world over? On an average, how much solar power is received on the surface of the earth at noon during a bright sunny day? 27. What are the prospects of wind and biomass energy? 28. Comment on the prospects of fossil fuels in India. 29. What is the status of non-conventional energy sources in India and what are their future prospects? 30. Comment on the growth of the energy sector in India. 31. Comment on the rural electrification plans of the government of India. 32. Discuss different renewable sources of energy with special reference to the Indian contexto (UPTU Lucknow 2003-04) 33. Describe the main features of various types of renewable and non-renewable energy resources and explain the importance of non-conventional energy sources in the context of global warming. (UPTU Lucknow 2007-08)

1.

Find the coefficient of performance and heat transfer rate in the condenser of a refrigerator in kJ/h which has a refrigeration capacity of 12,000 kJ/h. The power input to the Carnot engine driving the compressor is 0-75 kW. (Ans. 4.44,14,700 kJ/h)

1.

Which parameter is used as an index for the standard of living of the people of a country? (a) Industrial production (b) Number of vehicles per house (c) Per capita energy consumption (d) Population density What is the per capita electrical energy consumption of India? (a) 100 kWh/year (b) 150 kWh/year (c) 400 kWh/year (d) 700 kWh/year

2.

3. Which year is said to be the starting point for large scale planning of renewable energy globally? (a) 1973 (b) 1942 (c) 1850 (d) 1991 4. What is the percentage share of fossil fuel in the global consumption of primary energy? (a) 86% (b) 50% (c) 10% (d) 99% 5. Out of thermal, electrical, mechanical and chemical, which energy form is considered as top grade energy? (a) Mechanical (b) Chemical (c) Thermal (d) Electrical

Fundamentals of Energy-Science and Technology

t.~

~

6. Out of energy, economy and environment (a) only energy and environment are related (b) only energy and economy are related (c) all the three are interrelated (d) all the three are independent 7. Global warming is mainly caused due to (a) emission of heat from engines (b) emission of CO2 due to buming of fossil fuels (c) use of nuclear energy (d) air pollution 8. Use of nuclear energy is opposed due to (a) rapid depletion of nuclear uranium reserves (b) its high cost (c) ecological imba!ance caused due to its use (d) possibility of accident and radioactive pollution due to nuclear waste 9. Global warming would lead to (a) increase of agriculture production (b) acid rains (c) change of climatic pattem and its severity (d) increase in the efficiency of heat engines 10. What is the energy density of petrol? (a) 100MJ/kg (b) 51MJ/kg 11. What percentage (a) 20%

13. The most desirable option for energy farming of bio-diesel is the cultivation of suitable plants on (a) good fertile land of the country (b) roof tops of buildings (c) sea (d) marginal and fallow land, not suitable for normal agriculture 14. For a reversible adiabatic process, the change in entropy is (a) zero (b) minimum (c) infinite (d) 15. The processes of a Carnot cycle are (a) two adiabatic and two constant volume (b) two isothermal and two constant volume (c) two adiabatic and two isothermal (d) two constant volume and two constant pressure 16. In a (a) (b) (c) (d) Carnot engine, temperature temperature temperature temperature when working fluid gives heat to the sink, the of the sink increases of the source deceases of both the source and the sink decreases of the sink remains the same unity

17. The efficiency of an ideal Carnot engine depends on (a) the working substance (b) the temperature of both the source as well as sin k

,
Non-conventional Energy Resources

(e) (d)

on the temperature on the construction

of the sink only of the engine

18. The Rankine cycle efficiency of a good steam power plant may be in the range of (a) 35-45% (b) 90-95% (e) 15-20% (d) 70-80% 19. The Rankine cycle efficiency of a steam power plant (a) improves in winter as compared to that in summer (b) improves in summer as compared to that in winter (e) is unaffected by climatic conditions . (d) none of the above 20. Regenerative cycle thermal efficiency of a Rankine cycle (a) is same as a simple Rankine cycle thermal efficiency (b) is always less than that of a simple Rankine cycle thermal efficiency (e) is always greater than that of a simple Rankine cycle thermal efficiency (d) none of the above